Method and machine for stripping electric cables

ABSTRACT

A method of stripping electric cables (C) is disclosed comprising the following steps: arranging the end (E 1,  E 2 ) of a cable (C) to be stripped inside a stripping unit ( 1 ); cutting circumferentially the sheath (C 1,  C 2 ) covering the end (E 1,  E 2 ) of the cable (C) for at least a portion of the thickness and at least a portion of the perimeter of the sheath (C 1,  C 2 ); separating the sheath (C 1,  C 2 ) covering the end (E 1,  E 2 ) of the cable (C). The circumferential cut of the sheath (C 1,  C 2 ) is carried out by combining an action of incision of the sheath (C 1,  C 2 ) with an action of rotation of the cable (C).

[0001] The present invention relates to a method for stripping electriccables and a stripping machine to carry out said method.

[0002] It is well known that proper stripping machines are used to stripthe ends of electric cables, carrying out such stripping operation in anautomatic or semiautomatic way.

[0003] The known stripping machines available on the market are providedwith blades with cutting profile put in motion by suitable driving meansmoving the blades one against the other and the cable arrangedtherebetween along a rectilinear direction orthogonal to the cableadvancement direction.

[0004] In order to carry out the stripping operation, the blades arelowered until they incise the sheath of the cable that is then advancedalong the longitudinal direction defined by its axes.

[0005] In this way the blades that are not yet inserted in the incisionmade in the sheath, act as resistant element and when the cable isadvanced they allow to unthread the sheath cut section.

[0006] The above mentioned machines of the prior art have however somedrawbacks.

[0007] A first drawback consists in that when the cutting profile of theblades is worn, a neat incision of the sheath cannot be obtained and itsseparation from the cable may result difficult.

[0008] This happens especially in the stripping machines carrying outalso shearing of the cables by using for the shearing operation the sameblades that are used for the stripping operation.

[0009] Another drawback consists in that if work is effected with bladeshaving a worn cutting edge, during incision the cable may be squeezedand therefore damaged especially when the cables are of soft materialand of small thickness.

[0010] The present invention aims at overcoming said drawbacks.

[0011] More particularly, a first object of the invention is to providea method to carry out stripping of electric cables allowing to improvethe quality of the sheath incision.

[0012] Another object of the method of the invention is to obtain a goodincision of the sheath even using blades with imperfectly sharpenedcutting edges.

[0013] A further object of the method of the invention is to obtain anoptimal incision of the sheath even on cables made of soft materials andof small thickness.

[0014] A last but not least object of the invention is to provide amachine allowing to carry out the above mentioned stripping method.

[0015] The foregoing objects are attained by a stripping method forelectric cables that according to the main claim comprises the followingsteps: arranging the end of at least a cable to be stripped inside astripping unit; cutting circumferentially the sheath covering said endof said cable for at least a portion of the thickness and at least aportion of the perimeter of said sheath; separating said sheath coveringsaid end from said cable, and wherein said circumferential cut of saidsheath is carried out combining at least an action of incision of saidsheath with at least an action of rotation of said cable.

[0016] According to a first operative mode, the circumferential cut ofsaid sheath comprises sequentially: a first incision of said sheath; arotation of said cable; a second incision of said sheath, where theaction of rotation of said cable starts when the first incision is endedand ends before starting the second incision.

[0017] According to a second operative mode, the circumferential cut ofsaid sheath starts before the rotation action and is continued duringthe rotation action.

[0018] According to the invention the above mentioned method is carriedout by a stripping machine for electric cables comprising a casing onwhich there are a stripping unit for said cable; driving means foradvancing said cable arranged upstream and downstream said strippingunit; at least a control and actuation microprocessor unit, and whereinsaid stripping unit comprises at least a cutting unit for incision ofthe sheath covering at least an end of said cable; at least a rotationunit receiving said cable and putting it in rotation around thelongitudinal axis defined by said cable when it is arranged in arectilinear position.

[0019] According to the embodiment that will be described hereinafter,the rotation unit comprises a cable blocking chuck arranged coaxiallyoutside said cable and coupled to driving means putting it in rotationaround the longitudinal axis defined by the cable when it is arranged ina rectilinear position.

[0020] The blocking chuck comprises in its turn a couple of oppositejaws coupled to driving means adapted to move them mutually one againstthe other to clamp the cable to be stripped therebetween.

[0021] The driving means to put in rotation said rotation unit as wellas the driving means to move said jaws, consist of fluidic actuatorspreferably but not necessarily pneumatic actuators.

[0022] Advantageously, use of the method of the invention and of thestripping machine with stripping unit provided with rotary chuck, allowto improve the cutting and stripping quality of cables of any kind.

[0023] Still advantageously, the stripping unit with rotary chuck may beapplied to stripping machines of any kind and therefore, for instance,to machines that carry out in addition to the cable stripping operation,also the shearing operation of the cable to obtain sections ofpredetermined length and possibly also stripping of the wiresconstituting the cable.

[0024] The foregoing objects and advantages will be better understood byreading the following description of a preferred embodiment of themethod of the invention and of the stripping unit to carry out themethod, by making reference to the accompanying sheets of drawing inwhich:

[0025]FIG. 1 is a general front view of the stripping machine of theinvention;

[0026]FIG. 2 shows a portion of the machine of FIG. 1;

[0027] FIGS. 3 to 9 show details of the machine of FIG. 1;

[0028] FIGS. 10 to 15 show different operative positions of the machineof FIG. 2; and

[0029]FIGS. 16 and 17 show details of FIG. 15.

[0030] The machine of the invention is a shearing-stripping machineshown in FIG. 1 where it is indicated generally with character M and isprovided with a stripping unit generally indicated with referencenumeral 1.

[0031] The machine comprises a casing 2 supporting the stripping unit 1to be generally seen also in FIG. 2; driving means generally indicatedwith numeral 5 that can be seen besides FIGS. 1 and 2 also in FIGS. 10to 15, adapted to advance the cable C along a longitudinal direction X;and a control and actuation microprocessor unit generally indicated withnumeral 8.

[0032] Preferably but not necessarily the shearing-stripping machine ofthe invention is also provided with an alignment and stripping unitgenerally indicated with numeral 4 for the wires F constituting thecable C, shown in detail in FIGS. 16 and 17.

[0033] With particular reference to FIG. 2, one can see that the drivingmeans 5 comprise a first driving unit generally indicated with numeral6, introducing the cable C to the stripping unit 1 and a second drivingunit generally indicated with numeral 7, extracting said cable C fromthe stripping unit 1.

[0034] The shearing-stripping machine M comprises also a cable guideroller inlet 9 followed by a gauging unit 10 and a cable guiding inlet12 enhancing grip of cable C by the first driving unit 6.

[0035] Downstream the first driving unit 6 there is an intermediatecable guide 13 comprising a tubular member 13 a having an end 13 bpivoted though a pin 13 c to the movable member 13 d of a first actuator13 e fixed to the casing 2 of the machine; a second actuator 14 alsofixed to the casing 2 of the machine, having the movable member 14 apivoted in an intermediate position to the tubular member 13 a.

[0036] Through said actuators, the tubular member 13 a therefore may betranslated horizontally and rotated around the pin 13 c.

[0037] According to the invention the stripping unit 1 comprises acutting unit 15 for incision of said sheath covering at least an end E1,E2 of said cable C; a rotation unit 16 receiving said at least an endE1, E2 of said cable C and putting it into rotation around thelongitudinal axis X that said cable C defines when it is arranged in arectilinear position.

[0038] As to the cutting unit 15, one can see in FIG. 2 that itcomprises first blades 18, 19 to be seen in detail in FIGS. 8 and 9 andcomprising a couple of plates 20, 21 with planar surfaces 20, 21 ajuxtaposed one close to the other, each plate being provided withcutting edges 22, 23 having a V shaped profile with sharp edge 24, 25.

[0039] It is to be pointed out that the first blades may have also ashape different from that described and illustrated in the drawings.

[0040] The cutting unit 15 comprises also first driving and moving means50 to be seen in FIG. 7 adapted to move said blades 18, 19 in oppositevertical directions relative to the cable C arranged therebetween.

[0041] More particularly the driving and moving means 50 comprise amotor 51 putting in rotation a nut screw 52 having right-hand andleft-hand threads 52 a and 52 b respectively, connected to correspondingnut screws 53 a and 53 b that through blade holders 18 a, 19 a supportthe first blades 18 and 19 respectively. In this way, rotation of themotor 51 moves the first blades 18 and 19 to or away one another and thecable C whether the rotation occurs clockwise or anti-clockwise.

[0042] The rotation unit generally indicated with numeral 16 shown inFIG. 2 and in detail in FIGS. 3 to 6, comprises a rotary chuck generallyindicated with 30, whose body 30 a is supported by a flange 31 connectedto an actuator 32.

[0043] The actuator 32 has the body 32 a pivoted to the casing 2 of themachine while its rod 32 b has the end pivoted to said flange 31 so thatmovement of the rod 32 b generates rotation of the rotary chuck 30.

[0044] This chuck, more particularly, comprises a couple of jaws 33, 34between which the cable C is blocked, each jaw being supported by aslide, a second slide 35 and a first slide 36 respectively, sliding inthe body 30 a of the chuck and provided with a rack 37, 38.

[0045] The racks 37 and 38 are facing each other and mesh with a piniongear 39 while as shown in FIGS. 6b and 6 c, the jaws 33, 34 have aprofile in the form of a V shaped like a comb 33 a, 34 a for a betteradhesion to the cable C.

[0046] One of the slides, more particularly the first slide 36, isconnected to the rod 40 of a first pneumatic actuator 41 and when theactuator 41 is fed with pressurized air, the movement of its rod 40causes the mutual movement of the jaws 33, 34 to and away each other andtherefore blocking or release of the cable C whether the movement of therod 40 is in the direction of the arrow 40 a or in the oppositedirection of the arrow 40 b.

[0047] Indeed, interposition of the pinion gear 39 between the racks 37,38 allows to obtain always opposed movement of the jaws 33, 34.

[0048] A second actuator generally indicated with numeral 42 andsupported by the body 30 a of the rotary chuck 30, has also a rod 43co-operating with a screw 44 coupled in a nut screw 45 fixed to thesecond slide 35.

[0049] The screw 44 can be manually manipulated by the operator througha handle 44 a and adjusting the contrast against the rod 43 of thesecond actuator 42 it is possible to adjust the opening position of thejaws 33, 34 at will of the user.

[0050] As already mentioned, part of the shearing-stripping machine M ofthe invention is preferably but not necessarily also an alignment unitfor the wires F constituting the cable C, generally indicated withnumeral 4 and arranged upstream the stripping unit 1 as shown in FIG. 1and also in FIG. 2.

[0051] The alignment unit 4 is adapted to arrange the wires F of thecable C aligned on a generally horizontal plane juxtaposed one to theother before their stripping as shown in FIGS. 15 to 17.

[0052] More particularly, the alignment and stripping unit 4 accordingto a preferred embodiment comprises a couple of aligning jaws generallyindicated with 60 and consisting of two opposed jaws 61, 62 actuated byan actuator 63 and a couple of second opposed stripping blades 64, 65that are moved one against the other by actuators 66, 67 respectively.

[0053] To proceed to strip the cable C, the method of the inventionprovides for the following steps: arranging the end of the cable C to bestripped inside the stripping unit 1; cutting circumferentially thesheath covering said end of said cable C for at least a portion of thethickness and at least a portion of the perimeter of said sheath;separating said sheath covering said end from said cable where thecircumferential cut of said sheath is carried out combining at least anaction of incision of the sheath with at least an action of rotation ofthe cable.

[0054] For this purpose, first of all, it is necessary to introduce thecable C into the cable guide roller inlet 9 and then through the cableguide inlet 12 engaging the cable in the first driving unit 6 causing itto advance up to the position shown in FIG. 10.

[0055] In this position the front end E1 of the cable C is arranged inthe stripping unit 1 inside the rotary chuck 30 where it is arrangedbetween the jaws 33, 34.

[0056] At this point the stripping method provides for two differentoperative modes whether the cable is rigid so as to withstand rotationwithout twisting or is of soft material.

[0057] When the cable is of the rigid type, the stripping methodprovides for the following steps: clamping the end E1 of the cable Cbetween the jaws 33, 34 of the rotary chuck 30 by actuating the firstactuator 41; lowering the first blades 18, 19 until the sheath C1 of thecable C is incised at four zones Z1 opposite two-by-two indicated inFIGS. 3a and 3 c; lifting the belts forming the first driving unit 6 soas to release the cable C upstream the end E1; actuating the actuator 32so as to rotate the rotary chuck 30 from the position of FIG. 4 to thatof FIG. 3 to cause through the first blades 18, 19 the circumferentialincision of the sheath C1 shown in FIG. 3b; lowering again the belts ofthe driving unit 6 so as to clamp again the cable C; rotating the beltsof the driving unit 6 in the directions indicated by arrows of FIG. 11so as to move the cable C away from the stripping unit 1 along thedirection indicated by the arrow V1 to allow unthreading of the sectionC1 of the cable sheath; actuating the actuator 32 to return the rotarychuck 30 in the configuration of FIG. 4; and opening the jaws 33, 34 asshown in FIG. 6 up to the maximum opening of FIG. 6a to allow thedischarge by gravity of the sheath section C1.

[0058] As shown in FIG. 3, rotation of the rotary chuck 30 occurs for anangle preferably but not necessarily of 45 degrees which is sufficientto carry out cut of the sheath along its entire perimeter.

[0059] More particularly, in said FIGS. 6 and 6a one can see that thepiloted movement of the rod 43 of the second actuator 42 in contrastagainst the previously adjusted screw 44, allows to adjust the openingdegree of the jaws 33, 34 of the rotary chuck 30.

[0060] On the contrary, if the cable C is made of soft material andtherefore hardly adapted to withstand a cutting action by rotation assubject to twisting, the method provides for the following steps:clamping the end E1 of the cable C between the jaws 33, 34 of the rotarychuck 30 by actuating the first actuator 41; lowering the first blades18, 19 up to incision of the sheath C1 of the cable C at four zones Z1opposite two-by-two indicated in FIGS. 3a and 3 c; lifting the firstblades 18, 19 from the contact with the sheath C1 and also the beltsconstituting the first driving unit 6 from the contact with cable C;rotating the end E1 of cable C through rotation of the rotary chuck 30which is arranged in the configuration of FIG. 3; lowering again thefirst blades 18, 19 so as to incise the sheath C1 of cable C in fourfurther zones Z2 obtaining a generally octagonal cut shown in FIG. 3d;lowering again the belts of the driving unit 6 so as to block again thecable C; rotating the belts of the driving unit 6 in the directionsindicated by the arrows of FIG. 11 to move the cable C away from thestripping unit 1 along the direction indicated by arrow V1 and allowunthreading of the stretch C1 of the sheath of cable C; returning therotary chuck 30 to the configuration of FIG. 4; and opening the jaws 33,34 arranging them again in the final configuration shown in FIGS. 6a toallow discharge by gravity of the sheath C1.

[0061] With this second method twisting of the cable is avoided butseparation of the sheath C1 occurs in an easy way just as in thepreceding case in which the sheath is cut circumferentially. Indeed, theeight incisions Z1 and Z2 to be seen in FIG. 3d that are made in twosubsequent moments by the blades 18, 19 circumferentially on the cableC, carry out cut of the sheath substantially along its entire periphery.

[0062] In order to avoid overlapping of the cutting zones Z1 and Z2 itis advisable that the rotary chuck 30 does not rotate for more that 45degrees.

[0063] In order to strip also the rear end E2 of cable C, first of allit is necessary to shear to size the cable C obtaining a section of thedesired length.

[0064] This is obtained as shown in FIG. 12, by advancing the cable C inthe direction indicated by arrow V though the first driving unit 6 andthe second driving unit 7 and then lowering the first blades 18, 19, thecable is shorn so as to obtain the section of the desired length.

[0065] The section is then retracted through the second driving unit 7in the direction of arrow V1 until it is arranged in the position shownin FIG. 13 with the rear end E2 in position in the stripping unit 1.

[0066] Before the section of the cable shorn to size is retracted in thedirection of the arrow V1, by acting on the intermediate cable guide 13,the tubular member 13 a is lifted so as to release the stripping zone ofthe rear end E2.

[0067] For the incision of the sheath section C2, one proceeds in eitherof the previously described two operative modes according to the natureof the cable, taking into account that the section of cable C accordingto the need, must be blocked or made free to rotate by either lifting orlowering the belts of the second driving unit 7.

[0068] After having cut the sheath section C2, keeping the first blades18, 19 lowered in the cut made in the sheath, the cable section isadvanced again in the direction indicated by arrow V as shown in FIG.14, so as to unthread the sheath section C2 from the cable C andreleasing the wires F.

[0069] Therefore, these wires may in turn be stripped by intervention ofthe alignment and stripping unit 4 and more particularly of the secondblades 64, 65 after alignment of the wires by closing the jaws 61, 62 ofthe alignment chuck 60 as shown in FIGS. 15 to 17.

[0070] Obviously, the described stripping method may start fromstripping the rear end E2 of the section shorn to size and then proceedto stripping the front end E1.

[0071] In view of the foregoing one can understand that the method andthe stripping unit of the invention attain the intended objects.

[0072] As already mentioned the stripping unit of the invention mayconstitute an autonomous stripping unit of the ends of sections alreadyshorn to size or may be applied to a shearing-stripping machine of anykind available on the market.

[0073] Possible constructional versions that should be made to thestripping unit of the invention should be intended covered by thepresent patent when falling in the scope of the appended claims.

1) A stripping method for electric cables (C) comprising the followingsteps: arranging the end (E1, E2) of at least a cable (C) to be strippedinside a stripping unit (1); cutting circumferentially the sheath (C1,C2) covering said end (E1, E2) of said cable (C) for at least a portionof the thickness and at least a portion of the perimeter of said sheath(C1, C2); separating said sheath (C1, C2) covering said end (E1, E2)from said cable (C), wherein said circumferential cut of said sheath(C1, C2) is made combining at least an action of incision of said sheath(C1, C2) with at least an action of rotation of said cable (C). 2) Themethod according to claim 1 wherein said circumferential cut of saidsheath (C1, C2) comprises sequentially the following steps: a firstincision (Z1) of said sheath (C1, C2); a rotation of said cable (C); asecond incision (C2) of said sheath (C1, C2), wherein said rotationaction of said cable (C) starts when said first incision (C1) is endedand ends before starting said second incision (C2). 3) The methodaccording to claim 1 wherein said circumferential cut of said sheath(C1, C2) comprises the incision of said sheath (C1, C2) and rotation ofsaid cable (C1), where the rotation action of said cable (C) occursduring incision of said sheath (C1, C2). 4) A stripping machine (M) forelectric cables (C) adapted to carry out the stripping method accordingto claim 1 comprising a casing (2) on which there are a stripping unit(1) of said cable (C); driving means (5) to advance said cable (C)arranged upstream and downstream said stripping unit (1); at least acontrol and actuation microprocessor unit (8), wherein said strippingunit (1) comprises: at least a cutting unit (15) for incision of thesheath (C1, C2) covering at least an end (E1, E2) of said cable (C); atleast a rotation unit (16) receiving said at least an end (E1, E2) ofsaid cable (C) and putting it in rotation around the longitudinal axis(X) defined by said cable (C) when it is arranged in a rectilinearposition. 5) The stripping machine (M) according to claim 4 wherein saidrotation unit (16) comprises a rotary chuck (30) for blocking said end(E1, E2) of said cable (C), said rotary chuck (30) being arrangedcoaxially outside said cable (C) and being coupled to driving means (32)adapted to put it into rotation around said longitudinal axis (X)defined by said cable (C). 6) The stripping machine (M) according toclaim 5 wherein said rotary chuck (30) comprises a couple of oppositejaws (33, 34) between which said end (E1, E2) of said cable (C) to beblocked and rotated is arranged, said jaws (33, 34) being each fixed toa corresponding slide (35, 36) sliding inside the body (30 a) of saidrotary chuck (30), at least a first (36) of said slides (35, 36) beingassociated to driving means adapted to mutually move said slides and atleast a second (35) of said slides being associated to means adjustingthe opening of said jaws (33, 34). 7) The stripping machine (M)according to claim 6 wherein said driving means comprise: a couple ofracks (37, 38) associated to said slides (35, 36) and facing each other;a pinion gear (39) arranged between said rack and meshing therewith; afirst actuator (41) supported by the body (30 a) of said rotary chuck(30), having a movable member (40) fixed to a first (36) of said slidesadapted to move it along a rectilinear direction (40 a, 40 b). 8) Thestripping machine (M) according to claim 6 wherein said means adjustingthe opening of said jaws (33, 34) comprise a second actuator (42)supported by the body (30 a) of said rotary chuck (30) having themovable member (43) co-operating with a screw (44) coupled in a nutscrew (45) fixed to said second (35) of said slides. 9) The strippingmachine (M) according to claim 6 wherein each of said jaws (33, 34) hasat least a profile (33 a, 34 a) in the form of a V shaped like a comb.10) The stripping machine (M) according to claim 4 wherein said cuttingunit (15) comprises at least a couple of first blades (18, 19)associated to driving and moving means (50) adapted to put them inmotion along opposed directions orthogonal to said longitudinal axis (X)of said cable (C). 11) The stripping machine (M) according to claim 10wherein said first blades (18, 19) have opposite cutting edges (22, 23)in the form of a V. 12) The stripping machine (M) according to claim 4wherein it comprises an aligning and stripping unit (4) for said wires(F) constituting said cable (C), arranged upstream said stripping unit(1) for said cable (C). 13) The stripping machine (M) according to claim6 wherein said rotary chuck (30) makes a rotation of 45°.